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Aerosol black carbon (BC) is a short-lived climate pollutant. The poorly constrained provenance of tropical marine aerosol BC hinders the mechanistic understanding of extreme climate events and oceanic carbon cycling. Here, we collected PM 2.5 samples during research cruise NORC2016-10 through South China Sea (SCS) and Northeast Indian Ocean (NEIO) and measured the dual-carbon isotope compositions (δ 13 C- Δ 14 C) of BC using hydrogen pyrolysis technique. Aerosol BC exhibits six different δ 13 C- Δ 14 C isotopic spaces (i.e., isotope provinces). Liquid fossil fuel combustion, from shipping emissions and adjacent land, is the predominant source of BC over isotope provinces "SCS close to Chinese Mainland" (53.5%), "Malacca Strait" (53.4%), and "Open NEIO" (40.7%). C 3 biomass burning is the major contributor to BC over isotope provinces "NEIO close to Southeast Asia" (55.8%), "Open NEIO" (41.3%), and "Open SCS" (40.0%). Coal combustion and C 4 biomass burning show higher contributions to BC over "Sunda Strait" and "Open SCS" than the others. Overall, NEIO near the Bay of Bengal, Malacca Strait, and north SCS are three hot spots of fossil fuel-derived BC; the first two areas are also hot spots of biomass-derived BC. The comparable δ 13 C- Δ 14 C between BC in aerosol and dissolved BC in surface seawater may suggest atmospheric BC deposition as a potential source of oceanic dissolved BC.

Fire is an essential component of tropical savannas, driving key ecological feedbacks and functions. Indigenous manipulation of fire has been practiced for tens of millennia in Australian savannas, and there is a renewed interest in understanding the effects of anthropogenic burning on savanna systems. However, separating the impacts of natural and human fire regimes on millennial timescales remains difficult. Here we show using palynological and isotope geochemical proxy records from a rare permanent water body in Northern Australia that vegetation, climate, and fire dynamics were intimately linked over the early to mid-Holocene. As the El Niño/Southern Oscillation (ENSO) intensified during the late Holocene, a decoupling occurred between fire intensity and frequency, landscape vegetation, and the source of vegetation burnt. We infer from this decoupling, that indigenous fire management began or intensified at around 3 cal kyr BP, possibly as a response to ENSO related climate variability. Indigenous fire management reduced fire intensity and targeted understory tropical grasses, enabling woody thickening to continue in a drying climate., (© 2021. The Author(s).)

Archaeological data and demographic modelling suggest that the peopling of Sahul required substantial populations, occurred rapidly within a few thousand years and encompassed environments ranging from hyper-arid deserts to temperate uplands and tropical rainforests. How this migration occurred and how humans responded to the physical environments they encountered have, however, remained largely speculative. By constructing a high-resolution digital elevation model for Sahul and coupling it with fine-scale viewshed analysis of landscape prominence, least-cost pedestrian travel modelling and high-performance computing, we create over 125 billion potential migratory pathways, whereby the most parsimonious routes traversed emerge. Our analysis revealed several major pathways-superhighways-transecting the continent, that we evaluated using archaeological data. These results suggest that the earliest Australian ancestors adopted a set of fundamental rules shaped by physiological capacity, attraction to visually prominent landscape features and freshwater distribution to maximize survival, even without previous experience of the landscapes they encountered., (© 2021. This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply.)

Stable carbon and nitrogen isotope analyses are widely used to infer diet and mobility in ancient and modern human populations, potentially providing a means to situate humans in global food webs. We collated 13,666 globally distributed analyses of ancient and modern human collagen and keratin samples. We converted all data to a common "Modern Diet Equivalent" reference frame to enable direct comparison among modern human diets, human diets prior to the advent of industrial agriculture, and the natural environment. This approach reveals a broad diet prior to industrialized agriculture and continued in modern subsistence populations, consistent with the human ability to consume opportunistically as extreme omnivores within complex natural food webs and across multiple trophic levels in every terrestrial and many marine ecosystems on the planet. In stark contrast, isotope dietary breadth across modern nonsubsistence populations has compressed by two-thirds as a result of the rise of industrialized agriculture and animal husbandry practices and the globalization of food distribution networks., Competing Interests: The authors declare no competing interest., (Copyright © 2021 the Author(s). Published by PNAS.)

The peopling of Sahul (the combined continent of Australia and New Guinea) represents the earliest continental migration and settlement event of solely anatomically modern humans, but its patterns and ecological drivers remain largely conceptual in the current literature. We present an advanced stochastic-ecological model to test the relative support for scenarios describing where and when the first humans entered Sahul, and their most probable routes of early settlement. The model supports a dominant entry via the northwest Sahul Shelf first, potentially followed by a second entry through New Guinea, with initial entry most consistent with 50,000 or 75,000 years ago based on comparison with bias-corrected archaeological map layers. The model's emergent properties predict that peopling of the entire continent occurred rapidly across all ecological environments within 156-208 human generations (4368-5599 years) and at a plausible rate of 0.71-0.92 km year -1 . More broadly, our methods and approaches can readily inform other global migration debates, with results supporting an exit of anatomically modern humans from Africa 63,000-90,000 years ago, and the peopling of Eurasia in as little as 12,000-15,000 years via inland routes.

As tropical savannas are undergoing rapid conversion to other land uses, native C 3 -C 4 vegetation mixtures are often transformed to C 3 - or C 4 -dominant systems, resulting in poorly understood changes to the soil carbon (C) cycle. Conventional models of the soil C cycle are based on assumptions that more labile components of the heterogenous soil organic C (SOC) pool decompose at faster rates. Meanwhile, previous work has suggested that the C 4 -derived component of SOC is more labile than C 3 -derived SOC. Here we report on long-term (18 months) soil incubations from native and transformed tropical savannas of northern Australia. We test the hypothesis that, regardless of the type of land conversion, the C 4 component of SOC will be preferentially decomposed. We measured changes in the SOC and pyrogenic carbon (PyC) pools, as well as the carbon isotope composition of SOC, PyC and respired CO 2 , from 63 soil cores collected intact from different land use change scenarios. Our results show that land use change had no consistent effect on the size of the SOC pool, but strong effects on SOC decomposition rates, with slower decomposition rates at C 4 -invaded sites. While we confirm that native savanna soils preferentially decomposed C 4 -derived SOC, we also show that transformed savanna soils preferentially decomposed the newly added pool of labile SOC, regardless of whether it was C 4 -derived (grass) or C 3 -derived (forestry) biomass. Furthermore, we provide evidence that in these fire-prone landscapes, the nature of the PyC pool can shed light on past vegetation composition: while the PyC pool in C 4 -dominant sites was mainly derived from C 3 biomass, PyC in C3-dominant sites and native savannas was mainly derived from C 4 biomass. We develop a framework to systematically assess the effects of recent land use change vs. prior vegetation composition., (© 2020 by the Ecological Society of America.)

The magnitude of the terrestrial carbon (C) sink may be overestimated globally due to the difficulty of accounting for all C losses across heterogeneous landscapes. More complete assessments of net landscape C balances (NLCB) are needed that integrate both emissions by fire and transfer to aquatic systems, two key loss pathways of terrestrial C. These pathways can be particularly significant in the wet-dry tropics, where fire plays a fundamental part in ecosystems and where intense rainfall and seasonal flooding can result in considerable aquatic C export (ΣF aq ). Here, we determined the NLCB of a lowland catchment (~140 km 2 ) in tropical Australia over 2 years by evaluating net terrestrial productivity (NEP), fire-related C emissions and ΣF aq (comprising both downstream transport and gaseous evasion) for the two main landscape components, that is, savanna woodland and seasonal wetlands. We found that the catchment was a large C sink (NLCB 334 Mg C km -2  year -1 ), and that savanna and wetland areas contributed 84% and 16% to this sink, respectively. Annually, fire emissions (-56 Mg C km -2  year -1 ) and ΣF aq (-28 Mg C km -2  year -1 ) reduced NEP by 13% and 7%, respectively. Savanna burning shifted the catchment to a net C source for several months during the dry season, while ΣF aq significantly offset NEP during the wet season, with a disproportionate contribution by single major monsoonal events-up to 39% of annual ΣF aq was exported in one event. We hypothesize that wetter and hotter conditions in the wet-dry tropics in the future will increase ΣF aq and fire emissions, potentially further reducing the current C sink in the region. More long-term studies are needed to upscale this first NLCB estimate to less productive, yet hydrologically dynamic regions of the wet-dry tropics where our result indicating a significant C sink may not hold., (© 2020 John Wiley & Sons Ltd.)

Rationale: Rapid, reliable isolation of pyrogenic carbon (PyC; also known as char, soot, black carbon, or biochar) for the determination of stable carbon isotope (δ 13 C) composition and radiocarbon ( 14 C) dating is needed across multiple fields of research in geoscience, environmental science and archaeology. Many current techniques do not provide reliable isolation from contaminating organics and/or are relatively time-consuming. Hydrogen pyrolysis (HyPy) does provide reliable isolation of PyC, but the current methodology is time consuming., Methods: We explored the potential for subjecting multiple samples to HyPy analysis by placing up to nine individual samples in custom-designed borosilicate sample vessels in a single reactor run. We tested for cross-contamination between samples in the same run using materials with highly divergent radiocarbon activities (~0.04-116.3 pMC), δ 13 C values (-11.9 to -26.5‰) and labile carbon content. We determined 14 C/ 13 C using accelerator mass spectrometry and δ 13 C values using an elemental analyser coupled to a continuous flow isotope ratio mass spectrometer., Results: Very small but measurable transfer between samples of highly divergent isotope composition was detectable. For samples having a similar composition, this cross-contamination is considered negligible with respect to measurement uncertainty. For samples having divergent composition, we found that placing a sample vessel loaded with silica mesh adsorbent between samples eliminated measurable cross-contamination in all cases for both 14 C/ 13 C and δ 13 C values., Conclusions: It is possible to subject up to seven samples to HyPy in the same reactor run for the determination of radiocarbon content and δ 13 C value without diminishing the precision or accuracy of the results. This approach enables an increase in sample throughput of 300-600%. HyPy process background values are consistently lower than the nominal laboratory process background for quartz tube combustion in the NERC Radiocarbon Laboratory, indicating that HyPy may also be advantageous as a relatively 'clean' radiocarbon pre-treatment method., (© 2020 John Wiley & Sons, Ltd.)

The future response of the Antarctic ice sheet to rising temperatures remains highly uncertain. A useful period for assessing the sensitivity of Antarctica to warming is the Last Interglacial (LIG) (129 to 116 ky), which experienced warmer polar temperatures and higher global mean sea level (GMSL) (+6 to 9 m) relative to present day. LIG sea level cannot be fully explained by Greenland Ice Sheet melt (∼2 m), ocean thermal expansion, and melting mountain glaciers (∼1 m), suggesting substantial Antarctic mass loss was initiated by warming of Southern Ocean waters, resulting from a weakening Atlantic meridional overturning circulation in response to North Atlantic surface freshening. Here, we report a blue-ice record of ice sheet and environmental change from the Weddell Sea Embayment at the periphery of the marine-based West Antarctic Ice Sheet (WAIS), which is underlain by major methane hydrate reserves. Constrained by a widespread volcanic horizon and supported by ancient microbial DNA analyses, we provide evidence for substantial mass loss across the Weddell Sea Embayment during the LIG, most likely driven by ocean warming and associated with destabilization of subglacial hydrates. Ice sheet modeling supports this interpretation and suggests that millennial-scale warming of the Southern Ocean could have triggered a multimeter rise in global sea levels. Our data indicate that Antarctica is highly vulnerable to projected increases in ocean temperatures and may drive ice-climate feedbacks that further amplify warming., Competing Interests: The authors declare no competing interest., (Copyright © 2020 the Author(s). Published by PNAS.)

We present precipitation isotope data (δ 2 H and δ 18 O values) from 19 stations across the tropics collected from 2012 to 2017 under the Coordinated Research Project F31004 sponsored by the International Atomic Energy Agency. Rainfall samples were collected daily and analysed for stable isotopic ratios of oxygen and hydrogen by participating laboratories following a common analytical framework. We also calculated daily mean stratiform rainfall area fractions around each station over an area of 5° x 5° longitude/latitude based on TRMM/GPM satellite data. Isotope time series, along with information on rainfall amount and stratiform/convective proportions provide a valuable tool for rainfall characterisation and to improve the ability of isotope-enabled Global Circulation Models to predict variability and availability of inputs to fresh water resources across the tropics.

The timing, context and nature of the first people to enter Sahul is still poorly understood owing to a fragmented archaeological record. However, quantifying the plausible demographic context of this founding population is essential to determine how and why the initial peopling of Sahul occurred. We developed a stochastic, age-structured model using demographic rates from hunter-gatherer societies, and relative carrying capacity hindcasted with LOVECLIM's net primary productivity for northern Sahul. We projected these populations to determine the resilience and minimum sizes required to avoid extinction. A census founding population of between 1,300 and 1,550 individuals was necessary to maintain a quasi-extinction threshold of ≲0.1. This minimum founding population could have arrived at a single point in time, or through multiple voyages of ≥130 people over ~700-900 years. This result shows that substantial population amalgamation in Sunda and Wallacea in Marine Isotope Stages 3-4 provided the conditions for the successful, large-scale and probably planned peopling of Sahul.

The first peopling of Sahul (Australia, New Guinea and the Aru Islands joined at lower sea levels) by anatomically modern humans required multiple maritime crossings through Wallacea, with at least one approaching 100 km. Whether these crossings were accidental or intentional is unknown. Using coastal-viewshed analysis and ocean drift modelling combined with population projections, we show that the probability of randomly reaching Sahul by any route is <5% until ≥40 adults are 'washed off' an island at least once every 20 years. We then demonstrate that choosing a time of departure and making minimal headway (0.5 knots) toward a destination greatly increases the likelihood of arrival. While drift modelling demonstrates the existence of 'bottleneck' crossings on all routes, arrival via New Guinea is more likely than via northwestern Australia. We conclude that anatomically modern humans had the capacity to plan and make open-sea voyages lasting several days by at least 50,000 years ago.

Equatorial Southeast Asia is a key region for global climate change. Here, the Indo-Pacific Warm Pool (IPWP) is a critical driver of atmospheric convection that plays a dominant role in global atmospheric circulation. However, fluctuating sea-levels during the Pleistocene produced the most drastic land-sea area changes on Earth, with the now-drowned continent of Sundaland being exposed as a contiguous landmass for most of the past 2 million years. How vegetation responded to changes in rainfall that resulted from changing shelf exposure and glacial boundary conditions in Sundaland remains poorly understood. Here we use the stable carbon isotope composition (δ 13 C) of bat guano and High Molecular Weight n-alkanes, from Saleh Cave in southern Borneo to demonstrate that open vegetation existed during much the past 40,000 yrs BP. This location is at the southern equatorial end of a hypothesized 'savanna corridor' and the results provide the strongest evidence yet for its existence. The corridor would have operated as a barrier to east-west dispersal of rainforest species, and a conduit for north-south dispersal of savanna species at times of lowered sea level, explaining many modern biogeographic patterns. The Saleh Cave record also exhibits a strong correspondence with insolation and sea surface temperatures of the IPWP, suggesting a strong sensitivity of vegetation to tropical climate change on glacial/interglacial timeframes.

Rationale: Continuous measurement of stable O and H isotope compositions in water vapour requires automated calibration for remote field deployments. We developed a new low-cost device for calibration of both water vapour mole fraction and isotope composition., Methods: We coupled a commercially available dew point generator (DPG) to a laser spectrometer and developed hardware for water and air handling along with software for automated operation and data processing. We characterised isotopic fractionation in the DPG, conducted a field test and assessed the influence of critical parameters on the performance of the device., Results: An analysis time of 1 hour was sufficient to achieve memory-free analysis of two water vapour standards and the δ 18 O and δ 2 H values were found to be independent of water vapour concentration over a range of ≈20,000-33,000 ppm. The reproducibility of the standard vapours over a 10-day period was better than 0.14 ‰ and 0.75 ‰ for δ 18 O and δ 2 H values, respectively (1 σ, n = 11) prior to drift correction and calibration. The analytical accuracy was confirmed by the analysis of a third independent vapour standard. The DPG distillation process requires that isotope calibration takes account of DPG temperature, analysis time, injected water volume and air flow rate., Conclusions: The automated calibration system provides high accuracy and precision and is a robust, cost-effective option for long-term field measurements of water vapour isotopes. The necessary modifications to the DPG are minor and easily reversible., (Copyright © 2018 John Wiley & Sons, Ltd.)

Our ability to model global carbon fluxes depends on understanding how terrestrial carbon stocks respond to varying environmental conditions. Tropical forests contain the bulk of the biosphere's carbon. However, there is a lack of consensus as to how gradients in environmental conditions affect tropical forest carbon. Papua New Guinea (PNG) lies within one of the largest areas of contiguous tropical forest and is characterized by environmental gradients driven by altitude; yet, the region has been grossly understudied. Here, we present the first field assessment of aboveground biomass (AGB) across three main forest types of PNG using 193 plots stratified across 3,100-m elevation gradient. Unexpectedly, AGB had no direct relationship to rainfall, temperature, soil, or topography. Instead, natural disturbances explained most variation in AGB. While large trees (diameter at breast height > 50 cm) drove altitudinal patterns of AGB, resulting in a major peak in AGB (2,200-3,100 m) and some of the most carbon-rich forests at these altitudes anywhere. Large trees were correlated to a set of climatic variables following a hump-shaped curve. The set of "optimal" climatic conditions found in montane cloud forests is similar to that of maritime temperate areas that harbor the largest trees in the world: high ratio of precipitation to evapotranspiration (2.8), moderate mean annual temperature (13.7°C), and low intra-annual temperature range (7.5°C). At extreme altitudes (2,800-3,100 m), where tree diversity elsewhere is usually low and large trees are generally rare or absent, specimens from 18 families had girths >70 cm diameter and maximum heights 20-41 m. These findings indicate that simple AGB-climate-edaphic models may not be suitable for estimating carbon storage in forests where optimal climate niches exist. Our study, conducted in a very remote area, suggests that tropical montane forests may contain greater AGB than previously thought and the importance of securing their future under a changing climate is therefore enhanced., (© 2017 John Wiley & Sons Ltd.)

Reconstructing the dynamic response of the Antarctic ice sheets to warming during the Last Glacial Termination (LGT; 18,000-11,650 yrs ago) allows us to disentangle ice-climate feedbacks that are key to improving future projections. Whilst the sequence of events during this period is reasonably well-known, relatively poor chronological control has precluded precise alignment of ice, atmospheric and marine records, making it difficult to assess relationships between Antarctic ice-sheet (AIS) dynamics, climate change and sea level. Here we present results from a highly-resolved 'horizontal ice core' from the Weddell Sea Embayment, which records millennial-scale AIS dynamics across this extensive region. Counterintuitively, we find AIS mass-loss across the full duration of the Antarctic Cold Reversal (ACR; 14,600-12,700 yrs ago), with stabilisation during the subsequent millennia of atmospheric warming. Earth-system and ice-sheet modelling suggests these contrasting trends were likely Antarctic-wide, sustained by feedbacks amplified by the delivery of Circumpolar Deep Water onto the continental shelf. Given the anti-phase relationship between inter-hemispheric climate trends across the LGT our findings demonstrate that Southern Ocean-AIS feedbacks were controlled by global atmospheric teleconnections. With increasing stratification of the Southern Ocean and intensification of mid-latitude westerly winds today, such teleconnections could amplify AIS mass loss and accelerate global sea-level rise.

The effects of organic amendments and nitrogen (N) fertilizer on yield and N use efficiency of barley were investigated on a Nitisol of the central Ethiopian highlands in 2014. The treatments were factorial combinations of no organic amendment, biochar (B), compost (Com), Com+B and co-composted biochar (COMBI) as main plots and five N fertilizer levels as sub-plots, with three replicates. Application of organic amendment and N fertilizer significantly improved yield, with grain yield increases of 60% from Com+B+69kgNha(-1) at Holetta and 54% from Com+92kgNha(-1) at Robgebeya, compared to the yield from the maximum N rate. The highest total N uptake was obtained from Com+B+92kgNha(-1) at Holetta (138kgha(-1)) and Com+92kgNha(-1) at Robgebeya (101kgha(-1)). The agronomic efficiency (yield increase per unit of N applied, AE), apparent recovery efficiency (increase in N uptake per unit of N applied, ARE) and physiological efficiency (yield increase per unit of N uptake, PE) responded significantly to organic amendments and N fertilizer. Mean AE and ARE were highest at B+23kgNha(-1) at Holetta and at B+23 and B+46kgNha(-1) at Robgebeya. The PE ranged from 19 to 33kggrainkg(-1) N uptake at Holetta and 29-48kggrainkg(-1) N uptake at Robgebeya. The effects of organic amendments and N fertilizer on AE, ARE and PE were greater at Robgebeya than at Holetta. The enhancement of N use efficiency through application of organic amendments emphasizes the importance of balanced crop nutrition, ensuring that barley crops are adequately supplied with N and other nutrients. Overall, the integration of both organic and inorganic amendments may optimize N uptake efficiency and reduce the amount of N fertilizer required for the sustainable barley production in the long-term., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The Pleistocene global dispersal of modern humans required the transit of arid and semiarid regions where the distribution of potable water provided a primary constraint on dispersal pathways. Here, we provide a spatially explicit continental-scale assessment of the opportunities for Pleistocene human occupation of Australia, the driest inhabited continent on Earth. We establish the location and connectedness of persistent water in the landscape using the Australian Water Observations from Space dataset combined with the distribution of small permanent water bodies (springs, gnammas, native wells, waterholes, and rockholes). Results demonstrate a high degree of directed landscape connectivity during wet periods and a high density of permanent water points widely but unevenly distributed across the continental interior. A connected network representing the least-cost distance between water bodies and graded according to terrain cost shows that 84% of archaeological sites >30,000 y old are within 20 km of modern permanent water. We further show that multiple, well-watered routes into the semiarid and arid continental interior were available throughout the period of early human occupation. Depletion of high-ranked resources over time in these paleohydrological corridors potentially drove a wave of dispersal farther along well-watered routes to patches with higher foraging returns., Competing Interests: The authors declare no conflict of interest.

The study of palaeo-chronologies using fossil data provides evidence for past ecological and evolutionary processes, and is therefore useful for predicting patterns and impacts of future environmental change. However, the robustness of inferences made from fossil ages relies heavily on both the quantity and quality of available data. We compiled Quaternary non-human vertebrate fossil ages from Sahul published up to 2013. This, the FosSahul database, includes 9,302 fossil records from 363 deposits, for a total of 478 species within 215 genera, of which 27 are from extinct and extant megafaunal species (2,559 records). We also provide a rating of reliability of individual absolute age based on the dating protocols and association between the dated materials and the fossil remains. Our proposed rating system identified 2,422 records with high-quality ages (i.e., a reduction of 74%). There are many applications of the database, including disentangling the confounding influences of hypothetical extinction drivers, better spatial distribution estimates of species relative to palaeo-climates, and potentially identifying new areas for fossil discovery., Competing Interests: The authors declare no competing financial interests.

The addition of organic amendments to agricultural soils has the potential to increase crop yields, reduce dependence on inorganic fertilizers and improve soil condition and resilience. We evaluated the effect of biochar (B), compost (C) and co-composted biochar (COMBI) on the soil properties, crop yield and greenhouse gas emissions from a banana and a papaya plantation in tropical Australia in the first harvest cycle. Biochar, compost and COMBI organic amendments improved soil properties, including significant increases in soil water content, CEC, K, Ca, NO3, NH4 and soil carbon content. However, increases in soil nutrient content and improvements in physical properties did not translate to improved fruit yield. Counter to our expectations, banana crop yield (weight per bunch) was reduced by 18%, 12% and 24% by B, C and COMBI additions respectively, and no significant effect was observed on the papaya crop yield. Soil efflux of CO2 was elevated by addition of C and COMBI amendments, likely due to an increase in labile carbon for microbial processing. Our data indicate a reduction in N2O flux in treatments containing biochar. The application of B, C and COMBI amendments had a generally positive effect on soil properties, but this did not translate into a crop productivity increase in this study. The benefits to soil nutrient content, soil carbon storage and N2O emission reduction need to be carefully weighed against potentially deleterious effects on crop yield, at least in the short-term., (Copyright © 2016 Elsevier B.V. All rights reserved.)

During the Pleistocene, Australia and New Guinea supported a rich assemblage of large vertebrates. Why these animals disappeared has been debated for more than a century and remains controversial. Previous synthetic reviews of this problem have typically focused heavily on particular types of evidence, such as the dating of extinction and human arrival, and have frequently ignored uncertainties and biases that can lead to misinterpretation of this evidence. Here, we review diverse evidence bearing on this issue and conclude that, although many knowledge gaps remain, multiple independent lines of evidence point to direct human impact as the most likely cause of extinction., (© 2016 The Author(s).)

Soil quality decline represents a significant constraint on the productivity and sustainability of agriculture in the tropics. In this study, the influence of biochar, compost and mixtures of the two on soil fertility, maize yield and greenhouse gas (GHG) emissions was investigated in a tropical Ferralsol. The treatments were: 1) control with business as usual fertilizer (F); 2) 10 t ha(-1) biochar (B)+F; 3) 25 t ha(-1) compost (Com)+F; 4) 2.5 t ha(-1) B+25 t ha(-1) Com mixed on site+F; and 5) 25 t ha(-1) co-composted biochar-compost (COMBI)+F. Total aboveground biomass and maize yield were significantly improved relative to the control for all organic amendments, with increases in grain yield between 10 and 29%. Some plant parameters such as leaf chlorophyll were significantly increased by the organic treatments. Significant differences were observed among treatments for the δ(15)N and δ(13)C contents of kernels. Soil physicochemical properties including soil water content (SWC), total soil organic carbon (SOC), total nitrogen (N), available phosphorus (P), nitrate-nitrogen (NO3(-)N), ammonium-nitrogen (NH4(+)-N), exchangeable cations and cation exchange capacity (CEC) were significantly increased by the organic amendments. Maize grain yield was correlated positively with total biomass, leaf chlorophyll, foliar N and P content, SOC and SWC. Emissions of CO2 and N2O were higher from the organic-amended soils than from the fertilizer-only control. However, N2O emissions generally decreased over time for all treatments and emission from the biochar was lower compared to other treatments. Our study concludes that the biochar and biochar-compost-based soil management approaches can improve SOC, soil nutrient status and SWC, and maize yield and may help mitigate greenhouse gas emissions in certain systems., (Copyright © 2015. Published by Elsevier B.V.)

Late Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemble-hindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world's most controversial context, and instead estimate that the megafauna disappeared Australia-wide ∼13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions.

The lack of capacity to monitor forest carbon stocks in developing countries is undermining global efforts to reduce carbon emissions. Involving local people in monitoring forest carbon stocks could potentially address this capacity gap. This study conducts a complete expert remeasurement of community-led biomass inventories in remote tropical forests of Papua New Guinea. By fully remeasuring and isolating the effects of 4,481 field measurements, we demonstrate that programmes employing local people (non-experts) can produce forest monitoring data as reliable as those produced by scientists (experts). Overall, non-experts reported lower biomass estimates by an average of 9.1%, equivalent to 55.2 fewer tonnes of biomass ha(-1), which could have important financial implications for communities. However, there were no significant differences between forest biomass estimates of expert and non-expert, nor were there significant differences in some of the components used to calculate these estimates, such as tree diameter at breast height (DBH), tree counts and plot surface area, but were significant differences between tree heights. At the landscape level, the greatest biomass discrepancies resulted from height measurements (41%) and, unexpectedly, a few large missing trees contributing to a third of the overall discrepancies. We show that 85% of the biomass discrepancies at the tree level were caused by measurement taken on large trees (DBH ≥50 cm), even though they consisted of only 14% of the stems. We demonstrate that programmes that engage local people can provide high-quality forest carbon data that could help overcome barriers to reducing forest carbon emissions in developing countries. Nonetheless, community-based monitoring programmes should prioritise reducing errors in the field that lead to the most important discrepancies, notably; overcoming challenges to accurately measure large trees.

Macroalgae are a productive resource that can be cultured in metal-contaminated waste water for bioremediation but there have been no demonstrations of this biotechnology integrated with industry. Coal-fired power production is a water-limited industry that requires novel approaches to waste water treatment and recycling. In this study, a freshwater macroalga (genus Oedogonium) was cultivated in contaminated ash water amended with flue gas (containing 20% CO₂) at an Australian coal-fired power station. The continuous process of macroalgal growth and intracellular metal sequestration reduced the concentrations of all metals in the treated ash water. Predictive modelling shows that the power station could feasibly achieve zero discharge of most regulated metals (Al, As, Cd, Cr, Cu, Ni, and Zn) in waste water by using the ash water dam for bioremediation with algal cultivation ponds rather than storage of ash water. Slow pyrolysis of the cultivated algae immobilised the accumulated metals in a recalcitrant C-rich biochar. While the algal biochar had higher total metal concentrations than the algae feedstock, the biochar had very low concentrations of leachable metals and therefore has potential for use as an ameliorant for low-fertility soils. This study demonstrates a bioremediation technology at a large scale for a water-limited industry that could be implemented at new or existing power stations, or during the decommissioning of older power stations., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Seaweed cultivation is a high growth industry that is primarily targeted at human food and hydrocolloid markets. However, seaweed biomass also offers a feedstock for the production of nutrient-rich biochar for soil amelioration. We provide the first data of biochar yield and characteristics from intensively cultivated seaweeds (Saccharina, Undaria and Sargassum--brown seaweeds, and Gracilaria, Kappaphycus and Eucheuma--red seaweeds). While there is some variability in biochar properties as a function of the origin of seaweed, there are several defining and consistent characteristics of seaweed biochar, in particular a relatively low C content and surface area but high yield, essential trace elements (N, P and K) and exchangeable cations (particularly K). The pH of seaweed biochar ranges from neutral (7) to alkaline (11), allowing for broad-spectrum applications in diverse soil types. We find that seaweed biochar is a unique material for soil amelioration that is consistently different to biochar derived from ligno-cellulosic feedstock. Blending of seaweed and ligno-cellulosic biochar could provide a soil ameliorant that combines a high fixed C content with a mineral-rich substrate to enhance crop productivity.

The isotope signatures registered in speleothems during tropical cyclones (TC) provides information about the frequency and intensity of past TCs but the precise relationship between isotopic composition and the meteorology of TCs remain uncertain. Here we present continuous δ18O and δ2H data in rainfall and water vapour, as well as in discrete rainfall samples, during the passage of TC Ita and relate the evolution in isotopic compositions to local and synoptic scale meteorological observations. High-resolution data revealed a close relationship between isotopic compositions and cyclonic features such as spiral rainbands, periods of stratiform rainfall and the arrival of subtropical and tropical air masses with changing oceanic and continental moisture sources. The isotopic compositions in discrete rainfall samples were remarkably constant along the ~450 km overland path of the cyclone when taking into account the direction and distance to the eye of the cyclone at each sampling time. Near simultaneous variations in δ18O and δ2H values in rainfall and vapour and a near-equilibrium rainfall-vapour isotope fractionation indicates strong isotopic exchange between rainfall and surface inflow of vapour during the approach of the cyclone. In contrast, after the passage of spiral rainbands close to the eye of the cyclone, different moisture sources for rainfall and vapour are reflected in diverging d-excess values. High-resolution isotope studies of modern TCs refine the interpretation of stable isotope signatures found in speleothems and other paleo archives and should aim to further investigate the influence of cyclone intensity and longevity on the isotopic composition of associated rainfall.

Rationale: Traditionally, stable isotope analysis of plant and soil water has been a technically challenging, labour-intensive and time-consuming process. Here we describe a rapid single-step technique which combines Microwave Extraction with Isotope Ratio Infrared Spectroscopy (ME-IRIS)., Methods: Plant, soil and insect water is extracted into a dry air stream by microwave irradiation within a sealed vessel. The water vapor thus produced is carried to a cooled condensation chamber, which controls the water vapor concentration and flow rate to the spectrometer. Integration of the isotope signals over the whole analytical cycle provides quantitative δ(18)O and δ(2) H values for the initial liquid water contained in the sample. Calibration is carried out by the analysis of water standards using the same apparatus. Analysis of leaf and soil water by cryogenic vacuum distillation and IRMS was used to validate the ME-IRIS data., Results: Comparison with data obtained by cryogenic distillation and IRMS shows that the new technique provides accurate water isotope data for leaves from a range of field-grown tropical plant species. However, two exotic nursery plants were found to suffer from spectral interferences from co-extracted organic compounds. The precision for extracted leaf, stem, soil and insect water was typically better than ±0.3 ‰ for δ(18)O and ±2 ‰ for δ(2) H values, and better than ±0.1 ‰ for δ(18)O and ±1 ‰ for δ(2) H values when analyzing water standards. The effects of sample size, microwave power and duration and sample-to-sample memory on isotope values were assessed., Conclusions: ME-IRIS provides rapid and low-cost extraction and analysis of δ(18)O and δ(2) H values in plant, soil and insect water (≈10-15 min for samples yielding ≈ 0.3 mL of water). The technique can accommodate whole leaves of many plant species., (Copyright © 2014 John Wiley & Sons, Ltd.)

Variations in leaf mass per unit area (Ma) and foliar concentrations of N, P, C, K, Mg and Ca were determined for 365 trees growing in 23 plots along a West African precipitation gradient ranging from 0.29 to 1.62m a-1. Contrary to previous studies, no marked increase in Ma with declining precipitation was observed, but savanna tree foliar [N] tended to be higher at the drier sites (mass basis). Generally, Ma was slightly higher and [N] slightly lower for forest vs savanna trees with most of this difference attributable to differences in soil chemistry. No systematic variations in [P], [Mg] and [Ca] with precipitation or between trees of forest vs savanna stands were observed. We did, however, find a marked increase in foliar [K] of savanna trees as precipitation declined, with savanna trees also having a significantly lower [K] than those of nearby forest. These differences were not related to differences in soil nutrient status and were accompanied by systematic changes in [C] of opposite sign. We suggest an important but as yet unidentified role for K in the adaption of savanna species to periods of limited water availability; with foliar [K] being also an important factor differentiating tree species adapted to forest vs savanna soils within the 'zone of transition' of Western Africa.

Measurement of soil-respired CO₂ at high temporal resolution and sample density is necessary to accurately identify sources and quantify effluxes of soil-respired CO₂. A portable sampling device for the analysis of δ(13)C values in the field is described herein. CO₂ accumulated in a soil chamber was batch sampled sequentially in four gas bags and analysed by Wavelength-Scanned Cavity Ring-down Spectrometry (WS-CRDS). A Keeling plot (1/[CO₂] versus δ(13)C) was used to derive δ(13)C values of soil-respired CO₂. Calibration to the δ(13)C Vienna Peedee Belemnite scale was by analysis of cylinder CO₂ and CO₂ derived from dissolved carbonate standards. The performance of gas-bag analysis was compared to continuous analysis where the WS-CRDS analyser was connected directly to the soil chamber. Although there are inherent difficulties in obtaining absolute accuracy data for δ(13)C values in soil-respired CO₂, the similarity of δ(13)C values obtained for the same test soil with different analytical configurations indicated that an acceptable accuracy of the δ(13)C data were obtained by the WS-CRDS techniques presented here. Field testing of a variety of tropical soil/vegetation types, using the batch sampling technique yielded δ(13)C values for soil-respired CO₂ related to the dominance of either C₃ (tree, δ(13)C=-27.8 to-31.9 ‰) or C₄ (tropical grass, δ(13)C=-9.8 to-13.6 ‰) photosynthetic pathways in vegetation at the sampling sites. Standard errors of the Keeling plot intercept δ(13)C values of soil-respired CO₂ were typically<0.4 ‰ for analysis of soils with high CO₂ efflux (>7-9 μmol m(-2) s(-1)).

Land-based aquaculture produces suspended solids in culture pond and settlement pond waters that could be harvested as a bioresource. Suspended solids were quantified, characterised and harvested from these two sources to assess their suitability for conversion to bioproducts. The suspended solids of settlement ponds were less concentrated (87.6±24.7mgL(-1)) than those of culture ponds (131.8±8.8mgL(-1)), but had a higher concentration of microalgae (27.5±4.0%) and consequently higher particulate organic carbon (24.8±4.7%) and particulate nitrogen (4.0±0.8%). The microalgal community also differed between sources with a higher concentration of fatty acids in the biomass from settlement ponds. Consequently, biochar produced from biomass harvested from settlement ponds was higher in organic carbon and nitrogen, with a lower cation exchange capacity. In conclusion, we characterised a renewable and potentially valuable bioresource for algal bioproducts derived from suspended solids in intensive land-based aquaculture., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Rationale: Pyrogenic carbon (C(P)) is an important component of the global carbon budget. Accurate determination of the abundance and stable isotope composition of C(P) in soils and sediments is crucial for understanding the dynamics of the C(P) cycle and interpreting records of biomass burning, climate and vegetation change in the past. Here we test hydrogen pyrolysis (hypy) as a new technique potentially capable of eliminating labile organic carbon (C(L)) from total organic carbon (C(T)) in a range of matrices in order to enable reliable quantification of both the C(P) component of C(T) and the stable carbon isotope composition of C(P) (δ(13)C(P))., Methods: We mixed C(P) at a range of concentrations with common C(P)-free matrices (C(L) = cellulose, chitin, keratin, decomposed wood, leaf litter, grass and algae) and determined the amount of residual carbon not removed by hydrogen pyrolysis (C(R)) as a ratio of C(T) (C(R)/C(T)). Mixing C(P) with a unique δ(13)C value provided a natural abundance isotope label from which to precisely determine the ratio of C(P) to residual C(L) remaining after hypy., Results: All C(P)-free matrices contained trace carbon after hypy, indicating that hypy does not remove all the C(L). However, there was a strong correlation between C(R)/C(T) and C(P)/C(T), viz. C(R)/C(T)= 1.02(C(P)/C(T)) + 4.0 × 10(-3), r(2) = 0.99, p <0.001, suggesting that only a small and reasonably constant fraction of C(L) remains after hypy. Uncertainties associated with the correction for contamination of C(R) by residual C(L) are minimal allowing for reliable determinations of both C(P) and δ(13)C(P) in many cases., Conclusions: Hydrogen pyrolysis appears to be a robust technique for estimating C(P) abundance and δ(13)C(P) across a range of materials. Nevertheless, caution is required in interpreting δ(13)C(P) values when C(P)/C(T) is low, with C(P)/C(T)>4% being required for the determination of the δ(13)C(P) values within an interpretable error under our experimental conditions., (Copyright © 2012 John Wiley & Sons, Ltd.)

Rationale: Quantifying the processes that control dissolved inorganic carbon (DIC) dynamics in aquatic systems is essential for progress in ecosystem carbon budgeting. The development of a methodology that allows high-resolution temporal data collection over prolonged periods is essential and is described in this study., Methods: A novel sampling instrument that sequentially acidifies aliquots of water and utilises gas-permeable ePTFE tubing to measure the dissolved inorganic carbon (DIC) concentration and δ(13)C(DIC) values at sub-hourly intervals by Cavity Ring-down spectrometry (CRDS) is described., Results: The minimum sensitivity of the isotopic, continuous, automated dissolved inorganic carbon analyser (ISO-CADICA) system is 0.01 mM with an accuracy of 0.008 mM. The analytical uncertainty in δ(13)C(DIC) values is proportional to the concentration of DIC in the sample. Where the DIC concentration is greater than 0.3 mM the analytical uncertainty is ±0.1‰ and below 0.2 mM stability is < ± 0.3‰. The isotopic effects of air temperature, water temperature and CO(2) concentrations were found to either be negligible or correctable. Field trials measuring diel variation in δ(13)C(DIC) values of coral reef associated sea water revealed significant, short-term temporal changes and illustrated the necessity of this technique., Conclusions: Currently, collecting and analysing large numbers of samples for δ(13)C(DIC) measurements is not trivial, but essential for accurate carbon models, particularly on small scales. The ISO-CADICA enables on-site, high-resolution determination of DIC concentration and δ(13)C(DIC) values with no need for sample storage and laboratory analysis. The initial tests indicate that this system can offer accuracy approaching that of traditional IRMS analysis., (Copyright © 2012 John Wiley & Sons, Ltd.)

Feral pigs (Sus scrofa) are an invasive species that disrupt ecosystem functioning throughout their introduced range. In tropical environments, feral pigs are associated with predation and displacement of endangered species, modification of habitat, and act as a vector for the spread of exotic vegetation and disease. Across many parts of their introduced range, the diet of feral pigs is poorly known. Although the remote location and difficult terrain of far north Queensland makes observing feral pig behavior difficult, feral pigs are perceived to seek refuge in World Heritage tropical rainforests and seasonally 'crop raid' into lowland sugarcane crops. Thus, identifying how feral pigs are using different components of the landscape is important to the design of management strategies. We used the stable isotope composition of captured feral pigs to determine the extent of rainforest and sugarcane habitat usage. Recently grown hair (basal hair) from feral pigs captured in remote rainforest indicated pigs met their dietary needs solely within this habitat. Stable carbon and nitrogen isotope values of basal hair from feral pigs captured near sugarcane plantations were more variable, with some individuals estimated to consume over 85% of their diet within a sugarcane habitat, while a few consumed as much as 90% of their diet from adjacent forested environments. We estimated whether feral pigs switch habitats by sequentially sampling δ(13)C and δ(15)N values of long tail hair from a subset of seven captured animals, and demonstrate that four of these individuals moved between habitats. Our results indicate that feral pigs utilize both sugarcane and forest habitats, and can switch between these resources.

A novel sampling device suitable for continuous, unattended field monitoring of rapid isotopic changes in environmental waters is described. The device utilises diffusion through porous PTFE tubing to deliver water vapour continuously from a liquid water source for analysis of δ¹⁸O and δD values by Cavity Ring-Down Spectrometry (CRDS). Separation of the analysed water vapour from non-volatile dissolved and particulate contaminants in the liquid sample minimises spectral interferences associated with CRDS analyses of many aqueous samples. Comparison of isotopic data for a range of water samples analysed by Diffusion Sampling-CRDS (DS-CRDS) and Isotope Ratio Mass Spectrometry (IRMS) shows significant linear correlations between the two methods allowing for accurate standardisation of DS-CRDS data. The internal precision for an integration period of 3 min (standard deviation (SD) = 0.1‰ and 0.3‰ for δ¹⁸O and δD values, respectively) is similar to analysis of water by CRDS using an autosampler to inject and evaporate discrete water samples. The isotopic effects of variable air temperature, water vapour concentration, water pumping rate and dissolved organic content were found to be either negligible or correctable by analysis of water standards. The DS-CRDS system was used to analyse the O and H isotope composition in short-lived rain events. Other applications where finely time resolved water isotope data may be of benefit include recharge/discharge in groundwater/river systems and infiltration-related changes in cave drip water.

The role of African savannahs in the evolution of early hominins has been debated for nearly a century. Resolution of this issue has been hindered by difficulty in quantifying the fraction of woody cover in the fossil record. Here we show that the fraction of woody cover in tropical ecosystems can be quantified using stable carbon isotopes in soils. Furthermore, we use fossil soils from hominin sites in the Awash and Omo-Turkana basins in eastern Africa to reconstruct the fraction of woody cover since the Late Miocene epoch (about 7 million years ago). (13)C/(12)C ratio data from 1,300 palaeosols at or adjacent to hominin sites dating to at least 6 million years ago show that woody cover was predominantly less than ∼40% at most sites. These data point to the prevalence of open environments at the majority of hominin fossil sites in eastern Africa over the past 6 million years.

This study presents baseline data on the physiochemical properties and potential uses of macroalgal (seaweed) biochar produced by pyrolysis of eight species of green tide algae sourced from fresh, brackish and marine environments. All of the biochars produced are comparatively low in carbon content, surface area and cation exchange capacity, but high in pH, ash, nitrogen and extractable inorganic nutrients including P, K, Ca and Mg. The biochars are more similar in characteristics to those produced from poultry litter relative to those derived from ligno-cellulosic feedstocks. This means that, like poultry litter biochar, macroalgal biochar has properties that provide direct nutrient benefits to soils and thereby to crop productivity, and will be particularly useful for application on acidic soils. However, macroalgal biochars are volumetrically less able to provide the carbon sequestration benefits of the high carbon ligno-cellulosic biochars., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Today, insular Southeast Asia is important for both its remarkably rich biodiversity and globally significant roles in atmospheric and oceanic circulation. Despite the fundamental importance of environmental history for diversity and conservation, there is little primary evidence concerning the nature of vegetation in north equatorial Southeast Asia during the Last Glacial Period (LGP). As a result, even the general distribution of vegetation during the Last Glacial Maximum is debated. Here we show, using the stable carbon isotope composition of ancient cave guano profiles, that there was a substantial forest contraction during the LGP on both peninsular Malaysia and Palawan, while rainforest was maintained in northern Borneo. These results directly support rainforest "refugia" hypotheses and provide evidence that environmental barriers likely reduced genetic mixing between Borneo and Sumatra flora and fauna. Moreover, it sheds light on possible early human dispersal events.

We present the results of a study testing the response of two saprophytic white-rot fungi species, Pleurotus pulmonarius and Coriolus versicolor, to charred biomass (charcoal) as a growth substrate. We used a combination of optical microscopy, scanning electron microscopy, elemental abundance measurements, and isotope ratio mass spectrometry ((13)C and (15)N) to investigate fungal colonisation of control and incubated samples of Scots Pine (Pinus sylvestris) wood, and charcoal from the same species produced at 300 degrees C and 400 degrees C. Both species of fungi colonise the surface and interior of wood and charcoals over time periods of less than 70 days; however, distinctly different growth forms are evident between the exterior and interior of the charcoal substrate, with hyphal penetration concentrated along lines of structural weakness. Although the fungi were able to degrade and metabolise the pine wood, charcoal does not form a readily available source of fungal nutrients at least for these species under the conditions used in this study.

A robust timeframe for the extant cave deposits at Liang Bua, and for the river terraces in the adjoining Wae Racang valley, is essential to constrain the period of existence and time of extinction of Homo floresiensis and other biota that have been excavated at this hominin type locality. Reliable age control is also required for the variety of artifacts excavated from these deposits, and to assist in environmental reconstructions for this river valley and for the region more broadly. In this paper, we summarize the available geochronological information for Liang Bua and its immediate environs, obtained using seven numerical-age methods: radiocarbon, thermoluminescence, optically- and infrared-stimulated luminescence (collectively known as optical dating), uranium-series, electron spin resonance, and coupled electron spin resonance/uranium-series. We synthesize the large number of numerical age determinations reported previously and present additional age estimates germane to questions of hominin evolution and extinction.

We report results obtained using a new technique developed to measure the stable-isotope composition of uric acid isolated from bird excreta (guano). Results from a diet-switch feeding trial using zebra finches suggest that the delta(13)C of uric acid in the guano equilibrates with the diet of the bird within 3 days of a change in diet, while the equilibration time for delta(15)N may be longer. The average carbon isotope discrimination between uric acid and food before the diet switch was +0.34 +/- 1 per thousand (1sigma) while after the diet switch this increased slightly to +0.83 +/- 0.7 per thousand (1sigma). Nitrogen isotope discrimination was +1.3 +/- 0.3 per thousand (1sigma) and +0.3 +/- 0.3 per thousand (1sigma) before and after the diet switch; however, it is possible that the nitrogen isotope values did not fully equilibrate with diet switch over the course of the experiment. Analyses of other chemical fractions of the guano (organic residue after uric acid extraction and non-uric acid organics solubilised during extraction) suggest a total range of up to 3 per thousand for both delta(13)C and delta(15)N values in individual components of a single bulk guano sample. The analysis of natural samples from a range of terrestrial and marine species demonstrates that the technique yields isotopic compositions consistent with the known diets of the birds. The results from natural samples further demonstrate that multiple samples from the same species collected from the same location yield similar results, while different species from the same location exhibit a range of isotopic compositions indicative of different dietary preferences. Given that many samples of guano can be rapidly collected without any requirement to capture specimens for invasive sampling, the stable-isotope analysis of uric acid offers a new, simple and potentially powerful tool for studying avian ecology and metabolism.

To estimate the relative contributions of woody and herbaceous vegetation to savanna productivity, we measured the 13C/12C isotopic ratios of leaves from trees, shrubs, grasses and the surface soil carbon pool for 22 savannas in Australia, Brazil and Ghana covering the full savanna spectrum ranging from almost pure grassland to closed woodlands on all three continents. All trees and shrubs sampled were of the C3 pathway and all grasses of the C4 pathway with the exception of Echinolaena inflexa (Poir.) Chase, a common C3 grass of the Brazilian cerrado. By comparing the carbon isotopic compositions of the plant and carbon pools, a simple model relating soil delta 13C to the relative abundances of trees + shrubs (woody plants) and grasses was developed. The model suggests that the relative proportions of a savanna ecosystem's total foliar projected cover attributable to grasses versus woody plants is a simple and reliable index of the relative contributions of grasses and woody plants to savanna net productivity. Model calibrations against woody tree canopy cover made it possible to estimate the proportion of savanna productivity in the major regions of the world attributable to trees + shrubs and grasses from ground-based observational maps of savanna woodiness. Overall, it was estimated that 59% of the net primary productivity (Np) of tropical savannas is attributable to C4 grasses, but that this proportion varies significantly within and between regions. The C4 grasses make their greatest relative contribution to savanna Np in the Neotropics, whereas in African regions, a greater proportion of savanna Np is attributable to woody plants. The relative contribution of C4 grasses in Australian savannas is intermediate between those in the Neotropics and Africa. These differences can be broadly ascribed to large scale differences in soil fertility and rainfall.

The potency of the oligosaccharides SiaLe(x), SiaLe(a), HSO(3)Le(x), and HSO(3)Le(a), their conjugates with polyacrylamide (PAA, 40 kD), and other monomeric and polymeric selectin inhibitors has been compared with that of the polysaccharide fucoidan. The following assay systems were used: 1) a 96-well assay based either on the use of recombinant E-, P-, and L-selectins or an analogous assay with natural P-selectin isolated from human platelets; 2) a platelet-based P-selectin cell assay; and 3) a rat model of peritoneal inflammation. IC(50) values for the neoglycoconjugate SiaLe(a)-PAA were 6, 40, and 85 microM for recombinant E-, P-, and L-selectins, respectively; all monomeric inhibitors were about two orders of magnitude weaker. PAA-conjugates, containing as a ligand tyrosine-O-sulfate (sTyr) in addition to one of the sialylated oligosaccharides, were the most potent synthetic blockers in vitro. Compared with fucoidan, the most potent known P- and L-selectin blocker, the bi-ligand glycoconjugate HSO(3)Le(a)-PAA-sTyr displayed similar inhibitory activity in vitro towards L-selectin and about ten times lower activity towards P-selectin. All of the tested synthetic polymers displayed a similar ability to inhibit neutrophil extravasation in the peritonitis model (in vivo) at 10 mg/kg. The data provide evidence that monomeric SiaLe(x) is considerably more effective as a selectin blocker in vivo than in vitro, whereas the opposite is true for fucoidan and the bi-ligand neoglycoconjugate HSO(3)Le(a)-PAA-sTyr.

The occurrence of heterotrophic CO(2) fixation by soil microorganisms was tested in several mineral soils differing in pH and two artificial soils (a mixture of silica sand, alfalfa powder, and nutrient medium inoculated with a soil suspension). Soils were incubated at ambient ( approximately 0.05 vol%) and elevated ( approximately 5 vol%) CO(2) concentrations under aerobic conditions for up to 21 days. CO(2) fixation was detected using either a technique for determining the natural abundance of (13)C or by measuring the distribution of labeled (14)C-CO(2) in soil and bacteria. The effects of elevated CO(2) on microbial biomass (direct counts, chloroform fumigation extraction method), composition of microbial community (phospholipid fatty acids), microbial activity (respiration, dehydrogenase activity), and turnover rate were also measured. Heterotrophic CO(2) fixation was proven in all soils under study, being higher in neutral soils. The main portion of the fixed CO(2) (98-99%) was found in extracellular metabolites while only approximately 1% CO(2) was incorporated into microbial cells. High CO(2) concentration always induced an increase in microbial activity, changes in the composition of the microbial community, and a decrease in microbial turnover. The results suggest that heterotrophic CO(2) fixation could be a widespread process in soils.

Excavations at Liang Bua, a large limestone cave on the island of Flores in eastern Indonesia, have yielded evidence for a population of tiny hominins, sufficiently distinct anatomically to be assigned to a new species, Homo floresiensis. The finds comprise the cranial and some post-cranial remains of one individual, as well as a premolar from another individual in older deposits. Here we describe their context, implications and the remaining archaeological uncertainties. Dating by radiocarbon (14C), luminescence, uranium-series and electron spin resonance (ESR) methods indicates that H. floresiensis existed from before 38,000 years ago (kyr) until at least 18 kyr. Associated deposits contain stone artefacts and animal remains, including Komodo dragon and an endemic, dwarfed species of Stegodon. H. floresiensis originated from an early dispersal of Homo erectus (including specimens referred to as Homo ergaster and Homo georgicus) that reached Flores, and then survived on this island refuge until relatively recently. It overlapped significantly in time with Homo sapiens in the region, but we do not know if or how the two species interacted.